Depends on whether you'll be terminating SSL on the load balancer or web servers...

In general, if your load balancer can handle it, then better to do it all there and take the load off the web servers. Also it allows quicker deployment of new servers as it's one less step to worry about.

Having said that, once you have your private key and ssl cert from the provider, you can back these up and use them wherever you like (on LBs or servers), so you won't be tied to one method or the other permanently.